Anatomically preserved Liquidambar-like infructescences (Hamamelidaceae) from the middle Miocene Yakima Canyon flora of Washington, USA

Thirty-one specimens of petrified Liquidambar-like infructescences (Hamamelidaceae) have been studied from the middle Miocene Yakima Canyon flora of central Washington State, USA. The infructesences are globose fruiting heads consisting of dense clusters with numerous fruits per head. Each fruit is a 2-carpelled capsule with each carpel containing 1-2 mature seeds and up to 10 variously shaped abortive ovules. Mature seeds are 1.5 mm high x 1.2 mm wide, winged, and triangular in cross section. Seed integuments have a prominent outer layer of palisade cells, a middle region of isodiametric cells, and an inner lining of tangentially elongate cells. These fossils are the first anatomically preserved reproductive remains of Liquidambar-like plants to be described from northwestern North America and demonstrate similarities both to Tertiary forms such as the European Eocene Steinhauera Presl and Neogene Liquidamber as well as extant forms of subfamily Liquidambaroideae (Hamamelidaceae).